Abstract

Recent studies show that the UK is one of the countries with the highest asthma prevalence worldwide. It has been suggested that the trend towards the reduction of domestic ventilation rates for energy-efficiency reasons has resulted in poor indoor air quality and may represent a causal factor for the high asthma prevalence in the UK.

This study firstly aims to assess whether a link exists between asthma and low ventilation rates in housing. Secondly, the study aims to establish the minimum ventilation rate required in a dwelling in order to control levels of moisture-related pollutants (dust mites, mould) and therefore reduce the number of respiratory hazards. The work was funded by the UK Government's Building Regulations Research Programme.

An extensive review was performed of the UK and overseas published information on the links between asthma and domestic ventilation rates. The study also included an analysis of existing UK data sets where respiratory health, mould growth and housing characteristics were surveyed. In addition, the study involved theoretical modeling of a typical UK dwelling, to predict the impact that changes in ventilation rates will have on house dust mite (HDM) in a bed and on mould growth.

The literature review has highlighted that most existing data is inadequate for conclusions to be drawn regarding the direct association between ventilation rates and respiratory problems. For moisture-related pollutants the literature offers some advice on the minimum ventilation rates required to reduce pollutants levels. The analysis of existing UK data sets has not revealed any significant direct links between ventilation, respiratory health and moisture-related pollutants. The results of the theoretical modeling indicate that in most cases 0.5 ach-1 is required to avoid mould growth but a significantly higher ventilation rate (0.8 ach-1) may be required to control mites’ growth.

Most current guidance on domestic ventilation is based on the assumption that if adequate ventilation is provided for avoiding mould growth, then other IAQ problems will be contained. This study indicates that this may not be the case. In order to fully evaluate the direct link between asthma and low ventilation rates in the UK, a large scale prospective study is needed, where indoor pollutants, respiratory health indicators, air- tightness and ventilation rates are all adequately measured.